Father John was a major voice in the Orthodox community and worked for the reunion of the three splinter groups into which the Russian Orthodox Church broke after the Russian Revolution. He was instrumental in the establishment of the Orthodox Church in America in 1970, and urged the various Orthodox Churches in the United States, which were ethnically based, to grow closer together in their shared faith. He frequently represented the Orthodox tradition in ecumenical gatherings, such as the Uppsala Assembly held in 1968 by the World Council of Churches, during his tenure as Chairman of its Commission on Faith and Order (1967-1975).

Father John's publications include the critical text and translation of Byzantine theologian Gregory Palamas (1959), as well as a number of books in the fields of theology and history, such as A Study of Gregory Palamas (French ed., 1959; Engl. 1964); The Orthodox Church (1963); Orthodoxy and Catholicity (1966); Christ in Eastern Christian Thought (1969); Byzantine Theology (1973); Marriage, an Orthodox Perspective (1975); Living Tradition (1978); Byzantium and the Rise of Russia (1980); The Byzantine Legacy in the Orthodox Church (1981); Catholicity and the Church (1983); and Imperial Unity and Christian Divisions: The Church 450-680 AD (1989). His books have been published in a number of languages, including French, German, Italian, Russian, Greek, Finnish, Spanish, Dutch, Japanese, Serbian, and Polish.

The seminary community honors his memory every September at the annual Father John Meyendorff Memorial Lecture and especially remember him today, the day of his passing from death to life eternal.